Skip biquadratic resampling if volumetric fog filtering is on (saves 0.4ms)

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -106,6 +106,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Replaced the Density Volume Texture Tool with the new 3D Texture Importer.
 - Rename Raytracing Node to Raytracing Quality Keyword and rename high and low inputs as default and raytraced. All raytracing effects now use the raytraced mode but path tracing.
 - Moved diffusion profile list to the HDRP default settings panel.
+- Skip biquadratic resampling of vbuffer when volumetric fog filtering is enabled.
 
 ## [10.0.0] - 2019-06-10
 

com.unity.render-pipelines.high-definition/Runtime/Lighting/AtmosphericScattering/AtmosphericScattering.hlsl

@@ -277,6 +277,7 @@ void EvaluateAtmosphericScattering(PositionInputs posInput, float3 V, out float3
 
         if (_EnableVolumetricFog != 0)
         {
+            bool doBiquadraticReconstruction = _VolumetricFilteringEnabled == 0; // Only if filtering is disabled.
             float4 value = SampleVBuffer(TEXTURE3D_ARGS(_VBufferLighting, s_linear_clamp_sampler),
                                          posInput.positionNDC,
                                          fogFragDist,
@@ -285,7 +286,7 @@ void EvaluateAtmosphericScattering(PositionInputs posInput, float3 V, out float3
                                          _VBufferLightingViewportLimit.xyz,
                                          _VBufferDistanceEncodingParams,
                                          _VBufferDistanceDecodingParams,
-                                         true, true, false);
+                                         true, doBiquadraticReconstruction, false);
 
             // TODO: add some slowly animated noise (dither?) to the reconstructed value.
             // TODO: re-enable tone mapping after implementing pre-exposure.

com.unity.render-pipelines.high-definition/Runtime/Lighting/AtmosphericScattering/Fog.cs

@@ -164,6 +164,8 @@ void UpdateShaderVariablesGlobalCBFogParameters(ref ShaderVariablesGlobal cb, HD
             cb._HeightFogExponents = new Vector2(1.0f / H, H);
             cb._HeightFogBaseHeight = crBaseHeight;
             cb._GlobalFogAnisotropy = anisotropy.value;
+
+            cb._VolumetricFilteringEnabled = filter.value ? 1 : 0;
         }
     }
 

com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariablesGlobal.cs

@@ -129,7 +129,7 @@ unsafe struct ShaderVariablesGlobal
         public float    _HeightFogBaseExtinction;
         public float    _HeightFogBaseHeight;
         public float    _GlobalFogAnisotropy;
-        public float    _Pad3;
+        public int      _VolumetricFilteringEnabled;
         public Vector2  _HeightFogExponents; // { 1/H, H }
         public float    _Pad4;
         public float    _Pad5;

com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariablesGlobal.cs.hlsl

@@ -60,7 +60,7 @@ GLOBAL_CBUFFER_START(ShaderVariablesGlobal, b0)
     float _HeightFogBaseExtinction;
     float _HeightFogBaseHeight;
     float _GlobalFogAnisotropy;
-    float _Pad3;
+    int _VolumetricFilteringEnabled;
     float2 _HeightFogExponents;
     float _Pad4;
     float _Pad5;